Photographic emulsions



Patented MarhlY, 1942 rnorocmrmc muLsroNs Wesley G. Lowe, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. 2., a corporation of New Jersey No Drawing. Application August 1, 19,40,

Serial No. 349,296

- 11 Claims. (01. 95 -7) This invention relates to non-gelatin photographic emulsions in which the silver. halide has been dispersed and which are sensitized by sulfur compounds.

Gelatin has ordinarily been employed as the protective colloid for the light-sensitive silver halides in photographic emulsions due to its ability to hold these salts in suspension, its good water permeability, its, insolubility in photographic developing solutions at ordinary temperatures andits ability to form a thin coating of the light-sensitive silver halide emulsion upon a film support. Gelatin, however, has some disadvantages, such as its susceptibility to attack by organisms and because of its natural source, variation in its properties. Other protective colloids have been suggested for use instead of gelatin and some of these have been satisfactory in particular connections. For instance, cellulose nitrate has been found useful in wet-plate processes. Compounds, having high molecular weight, have been found useful as protective colloids for silver halides and have been sufliciently permeable to admit of fairly rapid processing in the con-' ventional developing and fixing baths. The emulsions prepared, however, with some of these nonthe product is water soluble. Some of the most effective dispersing agents of this type arethose consisting of a hydroxy alkyl amine combined with a cellulose derivative, such as an ethanolgelatin carriers or protective colloids lack the speed which can be attained with sensitized gelatin emulsions.

One .object of my invention is to prepare non-gelatin photographic emulsions having a high sensitivity. Other objects of my invention will appear herein.

I have found that by preparing non-gelatin photographic emulsions in which the silver halide is prepared in an amino nitrogen silver halide dispersing agent, .and asulfur sensitizer is incorporated in that emulsion, that the resulting product-has properties as regards speed which parallel those of photographic emulsions prepared in gelatin. The emulsions in accordance with my invention are prepared by first precipitating the silver halide in an aqueous solution of. a dispersing agent containing amino nitrogen. The compounds, which are suitable for this purpose, must be either water soluble or soluble in a liquid containing a major proportion of water, must be non-diiiusible and of high molecular weight, and must be compatible with the protective colloid employed. It must, of course, have the power of preventing the agglomeration of the particles of silver halide when they form. Such substances will be referred to herein as amino-nitrogencontaining silver halide dispersing agents.

Among the' amino-nitrogen-containing silver halide dispersing agents may be mentioned the water-soluble amino cellulose compounds, such as those in which an alkyl amino is combined with cellulose acetate in such'proportions that combined with cellulose acetate, the alkylamine' Q may'be combined with cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate lactate or some other cellulose derivative which may be combined therewith. Compounds of this type and their preparation are described and claimed in an application of Delbert D. Reynolds and William O. Kenyon Serial No. 349,222, filed of even date. The water-soluble amino derivatives of other high molecular weight compounds, such as carbohydrates like starch, inulin, or a saccharide, such as maltose, come within this class.

I. The amino derivatives of resins, having the characteristics specified, are also suitable for use in this connection. For instance, the amino aectals of polyvinyl alcohol may be employed for this purpose. Examples of resins which are suitable in this connection are the dimethyl-aminobenzaldehyde acetals of polyvinyl alcohol. The materials or this nature, which may be employed, and their process of preparation are described and claimed in Swan application Serial No. 349,229, filed of even date. Any of the compounds listed in that application, providing they have the necessary properties as specified, are suitable for use. Any other amino-nitrogen-containing compounds; which come withinthe qualifications set out, are suitable for preparing emulsions in accordance with my invention.

As the protective colloid or carrier'for the silver halide, any of the non-gelatin materials found to be useful for this purpose may be employed. For example, the far-hydrolyzed cellulose esters, such as cellulose acetate having an acetyl content of 19-26%, may be employed. A

polyvinyl acetaldehyde, having a polyvinyl acetal content of at least and a polyvinyl alcohol content of at least 15%, as described and claimed in Fordyce application Serial No. 221,584 filed case of the hydrolyzed po 1 acetates, those having a vinyl acetate content within the range of 59-71% have been found to besuitable as carriers for light-sensitive silver halides in photographic emulsions. as described and claimed in "my applications Serial N08. 318,559 and 318,560 -filed February 12, 1940.

sensitized gelatin emulsions, are also useful in the preparing of photographic emulsions in accordance with my invention. The sulfur sensitizers may be added during the preparation of the emulsion or to the emulsion after it is prepared. One point at which it might be added is after the washing of the emulsion and Just before'coating it upon the support. If the sensitizer is added at this point, sometimes its effect is increased by heat treatment or "flnishing of the emulsion. Howeventhesulfur sensitizing compound may be added during the preparation of the emulsion and its eflect on speed and contrast may be increasedby heat treatment of the emulsion, such as after washing of the emulsion. The sulfur sensitizing may be applied either to washed or unwashed emulsions.

The following examples illustrate my invention:

Example I i 50 parts of a 1.5% solution of diethanolamin cellulose acetate in water was heated to 80 F. Solutions A and B, having a temperature of 80 It, were added simultaneously over a period of three minutes with rapid stirring.

Solution A is 10 parts of 50% aqueous silver nitrate. Solution 8 is 10 parts of 40% potassium bromide and 0.5 part of 25% potassium iodide in water.

60 parts of a 10% solution. of polyvinyl alcohol was added. The emulsion wu heated to 120 F. and one part of gallic acid in parts of ethyl as-vases and washed to a pH of 4.2.an'd mg or 8.0. It was then heated to 60C. for 30 minutes. An emulsion giving good speed and contrast resulted.

Example III 100 parts or a 1.5% solution of diethanolamine cellulose acetate was heated to 80 F. Solutions A and B at 80 F. were added simultaneously over a period of 3 minutes with rapid stirring.

Solution A. parts of 50% silver nitrate using water as the solvent.

Solution B.--20 parts of 40% potassium bromide and one part of potassium iodide using water as the solvent. 7

' emulsion was precipitated by stirring into water,

alcohol was stirred in. The emulsion was gelled until it set firmly and was then shredded and washed. The emulsion was melted and 0.5% of gallic acid in 2% parts of ethyl alcohol was added. The emulsion hadthe following con-,

pAg=7.8

I stants:

50 gram of emulsion were treated with 0, 0.1, 0.2 and 0.4 cc. of 10% potassium thiocyanatesolution respectively and heated for 30 minutes at .60 C. On testing, these emulsion samples showed speeds in the following order: 1, 4, s and s.

' Example 11 Silver halide was precipitated in a solution of diethanolaminc cellulose acetate in the manner described in Example I. Two parts of 10% potassium thiocyanate was added and the emulsion was heatedfor 20 minutes at 104 F. parts of a 10% solution of polyvinyl alcohol was added. The emulsion was heated to F. and 1% parts of gallic acid in 5 parts of ethyl alcohol was stirred in. The emulsion was gelled, shredded washed and pressed to a weight of parts. It was dissolved in a mixture of the following solvents:

105 parts of water 96 parts of acetone 36 parts of ethyl cellosolve 6 parts of monoacetin and sensitized with 10 parts of 2,3'-diethyl-4'-methyloxathiazolocarbocyanine iodide before coating. This emulsion on standing for 12 hours at room temperature underwent a marked speed increase and exhibited finally a speed 45 times greater than that obtained when no sulfur sensitizer was used in the formula.

The emulsions, prepared in accordance with my invention, may be coated upon a supporting material, such as paper, or on a film support, such as cellulose ester or resin sheeting, to give a photographic product which is highly suitable for use where an emulsion of good speed is required. The silver halide portion of the emulsion is ordinarily prepared by reacting together' a water solution of silver nitrate and an aqueous solution of an alkali-metal bromide, chloride or iodide or a mixture of any of these. The process is carried out under agitated conditions so that the particle size of the precipitate is minute.

The photographic silver halide emulsions of my invention may also be dye-sensitized in the same manner as are silver halide emulsions generally. This is ordinarily accomplished with my emulsions by thoroughly incorporating a small amount of sensitizing dye therein after the emulsion is prepared. 1 Examples of sensitizers, which may be employed in the emulsions described herein, are the cyanines or the sensitizing dyes disclosed in the following patents: U. S. 2,078,233, Brooker, April 27, 1937; U. 8. 2,166,730, White et al., July 18, 1939; U. 8. 2,186,608, Keyes, Jan. 9, 1940; and U. S. 2,165,339, Brooker, July 11, 1939. In preparing emulsions in accordance with my invention Ihave found that the gelled polyvinyl alcohols are very suitable for use.- For instance, in Examples I and II the polyvinyl alcohol was gelled with gallic acid to form an emulsion which could 'be readily washed. A further description of gelled polyvinyl alcohols, which are suitable emulsions, such as by employing a spreading machine to assure the formation of a uniform coatmg on the film support.

I claim:

1. A photographic silver halide emulsion containing a silver halide dispersed by an aminonitrogen dispersing agent selected from the'group consisting of the water-soluble amino carbohydrate dispersing agents and the water-soluble amino-resin dispersing agents, carried by a protective colloid selected from the group consisting of the organic acid esters of cellulose having an acyl content of 19-26%, the polyvinyl acetaldehyde acetals having a polyvinyl acetal content of at least 50% and a polyvinyl alcohol content acetals having a vinyl alcohol content of 45-60%,

the polyvinyl butyraldehyde acetals having a vinyl alcohol content of 60-80%, the polyvinyl alcohols and the polyvinyl acetates having a polyvinyl acetate content of 59-71%, and sensitized by a sulfur sensitizer.

2. A photographic silver halide emulsion containing-a silver halide dispersed by an aminonitrogen dispersing agent selected from the group consisting of the water-soluble amino carbohydrate dispersing agents and the water-soluble amino-resin dispersing agents, carried by polyvinyl alcohol as the protective colloid and sensitized by a sulfur sensitizer.

3'. A photographic silver halide emulsion containing a silver halide dispersed by an aminonitrogen dispersing agent selected from the group consisting of the water-soluble amino carbohydrate dispersing agents and the water-soluble amino-resin dispersing agents, carried .by a water-susceptible lower fatty acid ester of cellulose and sensitized by a sulfur sensitizer.

4. A photographic material which comprises a support having thereon a coating of a silver halide photographic emulsion comprising silver halide dispersed by an amino-nitrogen dispersing agent selected from the group consisting of the water-soluble amino carbohydrate dispersing agents and the water-soluble amino-resin dispersing agents, carried by a protective colloid selected from the group consisting of the organic acid esters of cellulose having an acyl content of 19-26%, the polyvinyl 'acetaldehyde acetals having a polyvinyl acetal content of at least 50% and a polyvinyl alcohol content of at least 15%, the polyvinyl propionaldehyde acetals having a vinyl-alcohol content of 45-60%, the polyvinyl polyvinyl acetates having a polyvinyl acetate content of 59-71%, and sensitized by a sulfur sensitizer.

6. A photographic film comprising a cellulose ester film base having a coating thereon of a silver halide photographic emulsion comprising least the polyvinyl propionaldehyde acetals having a vinyl alcohol content of -60%, the polyvinyl butyraldehyde acetals having a vinyl alcohol content of 60-80%, the polyvinyl alcohols and the polyvinyl acetates having a polyvinyl acetate content of 59-71%, and sensitized by a sulfur sensitizer.

7. A method of preparing a photographic silver halide emulsion which comprises preparing silver halide in an aqueous solution of an amino-nitrogen dispersing agent selected from the group consisting of the water-soluble amino carbohydrate dispersing agents and the water-soluble content of 19-26%, the polyvinyl acetaldehyde butyraldehyde acetals having a vinyl alcohol content of 60-80%, the polyvinyl alcohols and the polyvinyl acetates having a polyvinyl acetate content of 59-71%, and sensitized by a sulfur sensitizer. e

5. Av photographic paper comprising paper sheeting having a coating of a silver halide emulsion thereon which emulsion comprises a silver acetals having a polyvinyl acetal content of at least50% and a polyvinyl alcohol content of at least 15%, the polyvinyl propionaldehyde acetals having a vinyl alcohol content of 45-60%, the polyvinyl butyraldehyde acetals having a vinyl alcohol content of -80%, the polyvinyl alcohols and the polyvinyl acetates having a polyvinyl acetate content of 59-71% and a sulfur sensitizer.

8. A method of preparing a photographic silver halide emulsion which comprises preparing silver halide in an aqueous solution of an amino-nitrogen silver halide dispersing agent consisting of an alkyl amine combined with a lower fatty acid ester of, cellulose, followed by mixing the dispersionwith an aqueous solution of cellulose acetate having an acetyl content of.19-26% and a sulfur sensitizer. 9. A photographic silverhalide emulsion containing' silver halide dispersed by an aminonitrogen silver halide dispersing agent consisting of a hydroxyalkylamine combined with a lower fatty acid ester of cellulose, carried by a protective colloid essentially consisting of a cellulose acetate propionate having an acyl content'of 19-2Y5% and sensitized by a sulfur sensitizer.

10. A. photographic silver halide emulsion containing a silver halide dispersed by an ethanolamine cellulose acetate, carried by a protective colloid essentially consisting of a cellulose acetate sensitized. by a sulfur sensitizer.

11. A photographic silver halide emulsion containing a silver halide dispersed by an aminoof 19-26%, the polyvinyl acetaldehyde acetals butyraldehyde acetals having a vinyl alcohol content of 60-80%, the polyvinyl alcohols and the sensitizer.

nitrogen dispersing agent of a hydroxyalkylamine combined with a lower fatty acid ester of cellulose, carried by a protective colloid essentiallyconsisting of cellulose acetatehaving an acetyl content of 19-26% and sensitized by a sulfur wnsmr c,- Lows,

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